The present invention relates to a densitometer for photography which is used for measuring the density of a photo such as a color print, a negative film and a reversal film, and for obtaining data such as exposure time correction data (so-called the slope correction) for color printer. The densitometer of the present invention also is applicable to the measurement of density in color printing.
FIGS. 1 to 4 illustrate conventional photographic densitometers.
A densitometer A shown in FIG. 1 has a transmission light receiving chamber 2 mounted to a specimen table 1 and an arm 3 which extends above the specimen table 1. To the arm 3 is mounted a cylinder 4, which is vertically movable. The transmission light receiving chamber 2 accommodates 12 light-transmitting receiving elements 5, three for each of four colors of red, green, blue and visual colors, as well as the same number of filters 6. An illuminating lamp 9 is disposed at the center of the space in the cylinder 4. A light diffusion plate 10 such as an opal glass fits in a sampling aperture 2a in the upper wall of the transmission light receiving chamber 2.
For the purpose of conducting measurement by the densitometer A, a specimen 11 is placed on the specimen table 1 and the cylinder 4 is lowered manually so as to bring the lower end of the cylinder 4 into close contact with the specimen 11. During measuring the reflection density, the light reflected by the upper surface of the specimen 11 is received by reflection light receiving elements 7 through the filters 8. During the measurement of the transmission density, the light which has been transmitted through the specimen 11 is diffused by a scattering diffusion plate 10 and is then received by the transmission light receiving element 5 through the filters 6.
A densitometer B shown in FIG. 2 has a lamp 13 for measurement of transmission density, which is disposed to a specimen table 12. At the same time, a disk 17 is mounted to an arm 15 in such a manner as to be rotated manually by means of a catch 18. At the same time, an optical-guide cylinder 19 is mounted in such a manner as to be manually movable up and down. At the same time, a light-receiving element 20 is fixed at a predetermined position.
The measurement with this densitometer B is conducted by manually rotating the disk 17 to bring a desired filter 16 into alignment with the light-receiving element 20, while lowering the optical guide cylinder 19, with the specimen placed on the specimen table 12. In operation, the light from the lamp 13 for transmission is passed through the specimen and an aperture 14 so as to be received by the light-receiving element 20 through the filter 16. This densitometer B is capable of measuring only the transmission density.
A densitometer C shown in FIG. 3 has an arm 23 which is vertically swingable with respect to a base plate 22. The arm 23 carries a disk 25 incorporating a plurality of filters 24, in such a manner that the disk 25 can be rotated manually by means of a catch 26. The densitometer C also has a light-receiving element 27, an optical guide cylinder 28 and a lamp 29 for reflection. The light from the reflection lamp 29 is projected from a focusing head 31 through an optical fiber 30.
The measurement with this densitometer C is effected by placing a specimen 32 under an aperture 21, and swinging the arm 23 downward so as to bring the focusing head 31 into alignment with the aperture 21, while manually rotating the disk 25 to bring the desired filter into alignment with the light-receiving element. The light from the lamp 29 for reflection is transmitted through the optical fiber 30 and is passed through the aperture 21 so as to impinge upon the specimen 32. The light reflected by the specimen 32 is received by the light-receiving element 27 via an aperture 31a of the focusing head 31 and the optical guide cylinder 28. This densitometer C is capable of measuring only the reflection density. The output from the light-receiving element 27 is transmitted from an output terminal 33 to the external data processing device and is processed by, for example, a CPU.
The densitometer D of FIG. 4 has, as is the case of the densitometer C shown in FIG. 3, an arm 36 which is vertically swingable with respect to the base plate 35 having a ring 35a. In this arrangement, the light from the lamp 37 for reflection is projected onto a focusing head 39 through an optical fiber 38. The reflected light incident to the aperture 39a of the focusing head 39 is received by four light-receiving elements 42 through four reflected light transmitting optical fibers 40 and then through the respective filters 41. This densitometer D can measure the reflection density by itself and can display the density value.
The conventional densitometers A to D described above have the following shortcomings:
(1) The mounting method and the mounting work for mounting the light-receiving element and the filters are generally complicated, with the result that the cost becomes high.
(2) It is not possible to obtain a uniform light.
(3) These densitometers are not capable of conducting measurement for reversal films.
(4) Wide installation area is required and the cost therefore is high because separate devices for measuring the reflection density and transmission density must be placed.
(5) The machines are operated manually and thus operation thereof requires the special skill.
(6) It is not possible to automatically analyze the measured data.
(7) These densitometers are not designed for enabling data processing, display and external output for the purpose of management of development.
In view of the above-described shortcomings of the conventional machines, an object of the present invention is to make it possible to conduct, with a single densitometer having a single light-receiving element, all kinds of photographic density measurement such as measurement of the color negative film transmission density, color print reflection density, color reversal film transmission density, monochromatic film transmission density, monochromatic print reflection density and monochromatic reversal film transmission density, and also to enable the single densitometer to externally display and output development administration data by automatically analyzing and computing the measured data.